语法制导翻译

for循环语句翻译递归下降法输出三地址码/////////////#define MAX 100#include<iostream.h>#include<stdio.h>#include<string.h>char str[MAX];char ch;int turn;char strToken[MAX];int kind;int n=0;//存放strtoken[]元素的个数struct Word//结构体存放单词{int sort;char word[MAX];//存放strtoken[]的内容};//record[x]=new Word;Word *record[12];//放所有识别出来的单词，分别存放他们的编号以及字符串，x是其下标////////////////////词法分析///////////////////////int buffer()//载入{int i=0;cout<<"输入程序，以“#”作为结束标志。

"<<endl;for(int n=0;n<=MAX;n++){for(;i<=MAX;i++){scanf("%c",&str[i]);/////////////cin>>str[i]不可用，用C语言读入字符。

if(str[i]=='#')break;///////如果尾数为识别码#,则表示程序读完,跳出循环.}break;}return(i);bool IsLetter(char ch)///////////判断是否是字母{if(ch>=65&&ch<=90||ch>=97&&ch<=122)return(true);elsereturn(false);}bool IsDigit(char ch)//////////判断是否是数字{if(ch>=48&&ch<=57)return(true);elsereturn(false);}char GetChar(int i)///////读取字符{char ch;ch=str[i];return(ch);}char GetBC(char ch)////判断是不是空格或者换行，如果是，直接读取下一个字符直道不再空白为止{if(ch==32||ch==10){turn++;ch=GetChar(turn);ch=GetBC(ch);/////////递归实现return(ch);}elsereturn(ch);}void Concat()/////////////连接，即为strtoken[]赋值{strToken[n]=ch;n++;int Reserve()/////以单词为单位查找保留字，是则返回编码，不是则返回0，用来区分标志符和保留字{if(strcmp(strToken," DIM\0")==0)///////调用strcmp函数实现,return(1);else if(strcmp(strToken,"for\0")==0)return(2);else if(strcmp(strToken,"step\0")==0)return(3);else if(strcmp(strToken,"until\0")==0)return(4);else if(strcmp(strToken,"do\0")==0)return(5);elsereturn(6);}void clear(){n=0;}/////////////*语法递归分析*/////////////////int A(int * c,int & q){if(c[q++]==3){if(c[q]==7){ q++;return 1;}else {cout<<"step右部出错"<<endl;return 0;}}else {cout<<"error 'step'"<<endl;return 0;}}int B(int * b,int & o)if(b[o++]==4){if(b[o]==7){ o++;return 1;}else {cout<<"until右部出错"<<endl;return 0;}}else {cout<<"error 'until'"<<endl;return 0;}}int S2(int * d,int & h){if(d[h++]==6){if(d[h++]==8){if((d[h]==6||d[h]==7)) {h++; return 1;}else {cout<<"赋值语句右部出错"<<endl;return 0;}}else {cout<<"赋值语句缺少赋值运算符"<<endl;return 0;} }else {cout<<"赋值语句左部出错"<<endl;return 0;}}int S1(int * m,int & n){if(S2(m,n)){if(A(m,n)){if(B(m,n)) return 1;else return 0;}else return 0;}else return 0;}int S(int *a,int & z){if (a[z++]==2){if (S1(a,z)){if(a[z++]==5){{cout<<"succeed!"<<endl;return 1;}else return 0;}else {cout<<"error 'do'"<<endl; return 0;}}else return 0;}else {cout<<"error 'for'"<<endl; return 0;}}void main(){cout<<"*************产生式***************"<<endl;// for step until do i j =cout<<" S ->for S1 do S2"<<endl; // 编号2 3 4 5 6 7 8cout<<" S1 ->S2AB"<<endl;cout<<" S2 ->i=j"<<endl;cout<<" A ->stepj"<<endl;cout<<" B ->untilj"<<endl;int num;turn=0;num=buffer()-1;int x=0;//计识别的单词的个数for(;turn<=num;turn++)//总循环,ch存放刚读入的字符，strtoken[]存放已识别的标志付或保留字，turn是数组str[]的下标{ch=GetChar(turn);ch=GetBC(ch);if(IsLetter(ch)){while(IsLetter(ch)&&turn<=num||IsDigit(ch)&&turn<=num){Concat();ch=GetChar(++turn);}strToken[n]='\0';ch=NULL;//此ch不是标志符中的符号kind=Reserve();record[x]=new Word; record[x]->sort=kind;//12345或6 //cout<<kind; //测试cout<<"(";for(int i=0;i<n;i++){record[x]->word[i]=strToken[i];cout<<record[x]->word[i];//输出识别的标志符或保留字}cout<<","<<kind<<")"<<endl;record[x]->word[i]='\0';clear();x++;}else if(IsDigit(ch)){while(IsDigit(ch)&&turn<=num){Concat();ch=GetChar(++turn);}ch=NULL;turn=turn-1;kind=7;//////////////record[x]=new Word;record[x]->sort=kind;////////////////cout<<"(";for(int i=0;i<n;i++){record[x]->word[i]=strToken[i];cout<<record[x]->word[i];}cout<<","<<kind<<")"<<endl;record[x]->word[i]='\0';clear();x++;}else if(ch=='='){kind=8;///////record[x]=new Word;record[x]->word[0]='=';record[x++]->sort=kind;cout<<"(=,"<<kind<<")"<<endl;}elsecout<<"error input!"<<endl;}//////////////////////*语法分析*//////////////////int y;/*for(y=0;y<x;y++){cout<<record[y]->sort<<" ";//打印单词的编号。